過去二十年來，對雷射峰值功率的追求推動了強場物理與雷射核融合領域的進展，儘管多數成果仍集中於紫外至近紅外波段的固態雷射。雷射與電漿之間的交互作用不僅依賴聚焦強度，也仰賴雷射波長，因此為長波紅外光雷射—特別是二氧化碳 (CO2) 雷射—保留了獨特的研究利基。因其具備高有質動力、低電漿臨界密度與高電光轉換效率等優勢，使其成為粒子加速器與非熱平衡核融合等新興應用的有利選擇。然而，發展超快 CO2 雷射所面臨的一大挑戰是如何放大寬頻皮秒脈衝並同時抑制梳狀增益頻譜所引起的脈衝分裂。為此，本論文提出一種非線性種子注入的放大策略，可實現寬頻且近似單脈衝的放大。該方法基於創新的啾頻脈衝差頻 (CP-DFG)，利用次奈秒 1338 奈米單頻脈衝與寬頻 1540 奈米啾頻脈衝在 BGGSe 晶體中進行差頻。經光柵壓縮後，此種子系統可穩定輸出超過 60 微焦耳 3 皮秒的 10.2 微米脈衝，穩定度為 3.4%-rms，飄移率為 0.5%/小時。這種優異的穩定性得益於高穩定電流驅動器與泵浦雷射。其中 1338 奈米的二極體泵浦 Nd:YAG 雷射可穩定輸出 400 皮秒 6 毫焦耳的單頻脈衝，穩定度為0.7%-rms 。 10 微米種子脈衝寬度經由克爾偏振旋轉、條紋相機單擊發量測，以及脈衝光譜分析加以驗證。數值模擬顯示，該種子脈衝可於 CO2 放大器中誘發功率增寬與動態增益飽和，有效抑制脈衝分裂。基於上述成果，本論文進一步設計並建構一具電子束維持放電的高氣壓 CO2 放大器，並以 100 千伏級脈衝源驅動電子束。儘管該放大器仍在建構階段，本研究已為邁向亞洲首座兆瓦級 CO2 雷射系統奠定了堅實的基礎。;Pursuit of ever-increasing peak power in laser systems over the past two decades has led to remarkable advances in high-field physics and laser fusion, though much of this progress has centered around solid-state gain media and ultraviolet to near-infrared wavelengths. Applications involving laser–plasma interactions rely not only on the focused intensity but also on the laser wavelength. This leaves a niche for long-wavelength infrared (LWIR) lasers—particularly carbon dioxide (CO2) lasers—due to their large ponderomotive force, low plasma critical density, and high wall-plug efficiency. A major challenge in advancing ultrafast CO2 laser system lies in amplifying broadband picosecond pulses without pulse splitting caused by the comb-like gain spectrum. To overcome this challenge, a nonlinear-seeded amplification strategy that enables broadband quasi-single-pulse amplification is presented in this thesis. This approach involves the development of an energetic seed source based on a novel chirped-pulse difference-frequency generation (CP-DFG) scheme, where sub-nanosecond single-frequency 1338-nm pulses and broadband chirped 1540-nm pulses are mixed in a BGGSe crystal. After compression, this system routinely delivers 3-ps 10.2-µm pulses exceeding 60 µJ with 3.4%-rms fluctuation and 0.5%/hr drift. This superior stability is attributed to the highly stable current drivers and pump lasers. For the 1338-nm diode-pumped Nd:YAG laser delivering 400-ps 6-mJ pulses, the energy stability is 0.7%-rms. Single-shot measurements based on Kerr-polarization rotation, resolved by a streak camera and pulse spectrum analysis, confirmed the picosecond pulse duration. Numerical modeling showed that such intense seeds can suppress pulse splitting via power broadening and dynamic gain saturation in CO2 amplifiers. On the basis of these results, this thesis presents the design and construction of a high-pressure electron-beam-sustained CO2 amplifier driven by a 100-kV-class pulser. While the amplifier is still under construction, this work establishes a solid foundation for realizing the first terawatt-class CO2 laser system in Asia.
